He has not dropped because their is little chance to bank off tour money this year (or next).
This is what I think too. I remember reading somewhere that apparently he likes to perform at festivals to sorta gauge the reaction and go from there. Since we're in a pandemic and shows are just coming back (despite whether we feel that's a good idea or not), he's probably holding off until then. It's possible that he had something ready to go last year, but just didn't drop it.
I’d bet that Kendrick probably cares less about a number single as much he does a number 1 ALBUM.
Kendrick is an album artist. He puts his all into the final product and he wants to make the best most cohesive project possible. Having his album go number 1 i’d bet means leagues more than just one song charting
Kendrick being an album artist is what people love most about him. Whenever you get something from Kendrick, you know it's going to be an actual body of work and not a bunch of songs that sounds good, but the cohesiveness isn't quite there (although there's nothing wrong with that, provided it's a mixtape or something that shouldn't be taken too seriously).
It's like when someone in a rapper's camp says that they have 10 albums worth of material. I'm sure they do, but how many of those songs are
Kendrick-level album worthy? Those songs might be great, but they may not live up to the standard he's aiming for or simply just don't fit on the project he's working on, so they stay unreleased (plus it's just unrealistic to release every good song you make).
On the flip side (and I say this with no disrespect intended to him), look at Logic. Logic will drop an album every year, but the projects as a whole don't always reflect his talent. Some songs don't sound fleshed out well enough, or sometimes the writing just isn't there. And then there's songs on that very same project that shows just how skilled he can actually be. But when he takes his time and really focuses in, you get an album like No Pressure.
Essentially, I think with music dropping so often, it can sometimes hamper the quality if you're not in that creative space. Current artists that are running things may drop more frequently, but I'd say there's a reason why the top rappers tend to take 2-3 years on average to drop an album. The question of Quality vs. Quantity basically, and while the best answer is "both", we sometimes forget that no two artists are the same, and the creative process is different for everyone. I think most people understand this with Kendrick and that's why they're more willing to wait. His previous bodies of work allow that sort of thing. That expectation wouldn't happen with Lil Baby or Cardi B, because that's a lot easier to make in a shorter period of time than a To Pimp A Butterfly or even DAMN.